The major objective of Phase I of the Trials of Hypertension Prevention is to test the feasibility and short-term effectiveness of nutritional-behavior, non-pharmacologic interventions on reducing or preventing an increase in diastolic blood pressure. Upon completion, Phase II will be underaken to test whether the prevalence and incidence of hypertension can be reduced by the non-pharmocologic intervention(s) selected as optimal from the Phase I experience. During the initial 9 month planning, the protocol, manual of operations and data forms will be developed, and there will be central training of key clinical personnel. Recruitment in three waves is planned over a 9 month period and follow-up will be 27-36 months. St. Louis University will conduct systematic work site screening at McDonnell Douglas Corporation (38,000 employees). Men and women, age 25-49 years, will be eligible for a second examination if their DBP is greater than or equal to 85-99 mm Hg in the absence of specified exclusion criteria. At screening examinations 2 and 3, the DBP must be in the range of 85-94 mm HG for eligibility. Other exclusion criteria will be applied. Volunteers will be randomly assigned (double-blind) to one of four interventions - sodium, potassium or calcium supplementation or a matching placebo. Approximately 50 participants will be in each group. All will participate in an initial 12 week intervention program designed to reduce dietary sodium intake (and total fat, saturated fat and dietary cholesterol). All participants will be given instruction in stress management and relaxation techniques. Special weight reduction groups will be formed to promote weight loss. A maintenance schedule will provide for a gradual decrease in contacts to every three months. The major end-point will be diastolic blood pressure change from baseline to follow-up. Between-group differences in change will be used to assess the randomized interventions, and the optimum treatment will be recommended for the Phase II study.